1. Field of the Invention
The present invention relates to a cylinder and a position detecting sensor, which makes it possible to prevent a liquid from being trapped on an outer surface of the cylinder thereby to avoid a sanitary problem.
2. Description of the Related Art
A hydraulic cylinder has heretofore been used as drive means for transferring and positioning workpieces or for driving various industrial machines. The hydraulic cylinder is provided with a cylinder tube and accessories including a switch attached to the cylinder tube, so as to meet various needs of a user, for example, so as to reduce the size and carry out various functions such as option setting. As a result, the hydraulic cylinder has a complicated contour.
However, when the conventional hydraulic cylinder described above is assembled in a food processing machine or the like, the complicated structure of the cylinder is liable to trap a liquid in the irregular surface such as a groove in the cylinder tube or a ridge or a rail for mounting a switch, after a rinsing or sterilizing operation with water or the like essential for the food processing machine. The residence of the liquid or the like in the irregular surface will result in multiplication of various germs. Thus, there is a sanitary problem caused by breeding of the various germs in the foods or workpieces of the food processing machine.
For this reason, there is a strong demand for a sanitary cylinder tube which makes it possible to prevent a liquid from residing on the outer surface by allowing the liquid to naturally fall down in drops.
Further, as with the hydraulic cylinder, a switch which is attached to the hydraulic cylinder for detecting the position of a reciprocating piston has the same sanitary problem.
The conventional switch (or the position detecting sensor) is desirably set at an arbitrary position on its stroke, for the usability of the hydraulic cylinder. The size of the switch has been reduced according as the size reduction of the hydraulic cylinder. In other industrial fields, the hydraulic cylinder body can be easily grooved thanks to the development in technique for molding an extruding member or the like. One method adopted for mounting the switch position adjusting mechanism is to mount the switch on the rail or groove formed on the hydraulic cylinder body by means of screws for enabling the size reduction and simple position adjustment.
Another conventional method is to fix the switch on the hydraulic cylinder body by winding a band directly around the outer periphery of a cylinder tube.
However, when the aforementioned conventional switch is attached to the hydraulic cylinder for use in conjunction with a food processing machine, the complicated shape of the switch invites the residence of the liquid. Therefore, as with the hydraulic cylinder, there is a strong demanded for a switch which has a high draining (dehydrating) ability of allowing the liquid to naturally fall in drops while retaining the conventional position detecting function.
Moreover, some switches attached to the cylinder tube are equipped with a detecting position adjusting mechanism capable of displacing the position of the piston to be detected. However, as compared with a switch having no detecting position adjusting mechanism, the conventional switch has a larger switch body since the detecting position adjusting mechanism is provided. Therefore, in the conventional switch, it is difficult to reduce its size and weight.
A general object of the invention is to provide a cylinder comprising a cylinder tube having the outer periphery formed of outwardly (convexly) curved surfaces expect upright surfaces and having chamfered portions so as to prevent a liquid from being trapped on the outer surface thereby to avoid sanitary problems.
A main object of the invention is to provide a position detecting sensor comprising a body having the outer periphery formed of curved portions curved convexly outward, and chamfered portions so as to prevent a liquid from being trapped on the outer surface thereby to avoid sanitary problems.
Another object of the invention is to provide a position detecting sensor which makes it possible to provide a detection position adjusting mechanism without enlarging a sensor body so as to reduce the size and weight thereof.
Still another object of the invention is to provide a cylinder which can reliably block invasion of a liquid or the like from the outside through a joint portion between a cylinder tube and a cover member.
The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken with reference to the accompanying drawings, in which the preferred embodiments of the invention are shown by way of illustrative examples.